Project Summary/Abstract The long-term objective of this project is to help cochlear-implant (CI) users achieve better speech understanding in noisy, real-world listening environments. The specific objective of the proposed research is to evaluate why speech repair (restoration) mechanisms are atypical or absent in this population. The proposed experiments measure how bottom-up acoustic factors and linguistic knowledge impact speech restoration mechanisms in adult CI users, and the extent to which restoration develops in child CI users. Aim 1 measures three possible underlying causes for atypical/absent restoration in adult CI users. Aim 1 will test the hypothesis that front-end preprocessing, specifically noise reduction algorithms, interacts with poor peripheral auditory health to reduce restoration capabilities, while access to semantic information (which allows the listener to utilize his or her linguistic knowledge) may act as a protective factor. Aim 2 measures the extent to which restoration ability develops in child CI users. Aim 2 will test the hypothesis that access to degraded input throughout language development will decrease opportunities to develop helpful speech repair strategies. Child CI users thus may be delayed in this development compared to normal-hearing children, overly relying on poor bottom-up acoustic information to understand speech. The training program involves learning to experimentally test child participants, developing new methodological skills by utilizing an eye-tracker paradigm, deepening understanding of CI processing and programming capabilities, and honing skills necessary to become an independent researcher in the field of hearing, namely becoming trained in stimuli creation, experimental software programming, and manuscript/grant preparation. The results from the proposed project will inform the development of CI sound processing strategies that will better promote speech repair. Individualized front-end preprocessing parameters, dependent on peripheral auditory health, could allow individual CI users to best access restoration mechanisms. Results will also identify potential therapy targets, like increasing vocabulary size, for strengthening restoration in child CI users. This knowledge will help alleviate the most common complaint among CI users: difficulty understanding speech in noisy listening conditions. Improving restoration abilities will promote easier communication in these more realistic, everyday listening environments.